Monitoring scales are used for monitoring package weights, particularly in the pharmaceutical and food industries. The packages to be monitored are delivered to an entry transport belt and from there are transferred to a weighing belt. As they pass over the weighing belt, the weight of the packages is dynamically determined by a load cell. After passing over the weighing belt, the packages are carried off by an exit belt situated downstream. Off-weight packages are identified by this dynamic weighing process, and a pushing device ejects the off-weight packages transverse to their direction of transport in the longitudinal direction.
In this dynamic weighing operation, vibrations are often induced in particular by the transfer of incoming packages from the entry belt to the weighing belt, and from the weighing belt to the exit belt. In addition, the operation of the pushing device is another source of vibrations. For the frame, this results in the difficult task of attempting to suppress these undesirable vibrations to the greatest extent possible. With regard to the relative stability required for suppression of vibrations, such known frames are in need of improvement.
Another problem is that contents of the packages to be weighed, which in particular may be liquid, granular, or powdered, may get on the frame as a result of unavoidable irregularities during the course of operations, and remain there. As the known frames often represent complex welded structures composed of metal braces extending in the longitudinal and transverse directions, the frames are very susceptible to soiling and are difficult to clean.
A frame exhibiting a somewhat simpler assembly structure is described in German Patent Application 103 57 982.6, which represents an improvement over the available prior art with regard to the above-referenced problems. In the cited application, the transverse part is designed in the shape of a flat plate, the main plane of which extends transverse to the longitudinal direction. Such a design of the transverse part satisfies some of the stability issues in the vertical direction despite its relatively small dimension in the longitudinal direction, since the corresponding vertical load acting on the supporting longitudinal part of the frame is substantially diverted from the flat plate, in the direction of the main plane thereof, to the floor. At the same time, for such a frame the horizontally running surface region of the transverse part is negligibly small, so that such a design is also advantageous for technical cleaning reasons. Furthermore, such a frame promotes suppression of undesirable vibrations whereby, depending on the requirements, the mass of the frame is modified by filling the longitudinal part with gravel, for example.
However, such a frame described in Patent Application 103 57 982.6 has not proven to be entirely satisfactory with regard to suppression of vibrations in the longitudinal direction (direction of the conveyor belt). Such vibrations occur in the longitudinal direction particularly when products that are transported on the transport belts supported by the frame experience a change in velocity during the transition from a customer-side transport belt to the frame-supported belts, by which the forces which then compensate for the pulse balance are transmitted to the frame.